SONAR (Sound Navigation and Ranging) uses underwater sound propagation to detect and locate submerged objects.
932
A tuning fork of frequency 500 Hz is sounded on a resonance tube. The first, second and third resonances are obtained at 17 cm, 52 cm and 67 cm respectively. The velocity of sound in m s^-1 is
For a pipe closed at one end f1 = v/(4L) = 336/(4×1) = 84 Hz.
937
A tuning fork of frequency 100 Hz when sounded with another tuning fork of unknown frequency produces 2 beats per second. On loading the tuning fork whose frequency is not known and sounding it together with the 100 Hz fork produces one beat per second. The frequency of the other tuning fork is:
Initial difference is 2 Hz so unknown is 102 or 98 Hz; loading decreases its frequency and yields a 1 Hz beat, which fits starting value 102 Hz reduced to 101 Hz, so initial frequency is 102 Hz.
938
When sound waves enter a different medium, the quantity that remains unchanged is
The quality or timbre of a note depends on the presence and relative strengths of overtones/harmonics.
940
If a particle is travelling with a speed of 0.9 of the speed of sound and is emitting radiations of frequency 1 kilohertz and moving towards the observer, what is its apparent frequency?
